Drivers: How to access "self"?
Using self in a driver is not as straight forward as thought, though it is really easy once you know where to put it. In short: In your driver, simply don't declare a variable, but use self in the expression itself to reference to the object. Check this screenshot here:



This driver is hooked up to the scale.y property of an object. The important bit here is to check Use Self as indicated in the upper screenshot, so Blender actually declares what object self is pointing to automatically.

Now you can copy and paste this driver to any other object, it will take the scale.x from there as a driving source.